The present invention relates generally to solar power tower generation systems. In particular, the invention relates to a solar power tower generation system with high operating temperatures.
There is a continuing demand for clean renewable energy sources, such as solar power. Solar power towers generate electric power from sunlight by focusing concentrated solar radiation on a tower-mounted receiver. Solar power tower systems typically include a “cold” storage tank, a solar receiver, heliostats, a “hot” storage tank, and an energy conversion system, such as a steam generator or turbine/generator set. In operation, a heat transfer fluid is pumped from the cold storage tank to the solar receiver. The heat transfer fluid can be any medium that has the capability to transfer heat and thermally maintain the heat in the medium, such as water, liquid metal, or molten salt.
The solar receiver is typically positioned 50 feet to 250 feet or more above ground and is heated by the heliostats. The heliostats redirect and concentrate solar radiation from the sun onto the solar receiver, which converts the redirected sunlight to thermal energy. The heat transfer fluid flows through receiver tubes of the solar receiver where it is heated by the concentrated solar energy. In the solar receiver, liquid metals have been used as the heat transfer fluid and can reach temperatures of approximately 1600 degrees Fahrenheit (° F.) and molten salts currently being used as the heat transfer fluid can reach temperatures of approximately 1100° F.
After the heat transfer fluid has been heated in the solar receiver, the heat transfer fluid flows into the hot thermal storage tank. The heat transfer fluid is then stored in the hot thermal storage tank until it is needed for electrical power generation. The hot thermal storage tank allows for electrical power production that is not concurrent with the availability of sunlight. When electrical energy is needed, the heated heat transfer fluid is pumped from the hot thermal storage tank and circulated through the energy conversion system. The heat transfer fluid transfers the heat within the energy conversion system. The energy conversion system can be, for example, a Rankine cycle conversion system or a Brayton cycle conversion system. After the heat has been removed from the heat transfer fluid, the heat transfer fluid is transported back to the cold storage tank for reuse. In general, the higher the temperature of the heat transfer fluid, the more efficient the solar tower power system. Thus, heat transfer fluids and systems capable of withstanding higher temperatures are desirable.